#include<stdio.h>
int main()
{  
    char ch;
    int sum=0;
    while(scanf("%c",&ch)==1)
    {
        if(ch=='\n')
        {
            break;
        }
        if(ch>='0'&&ch<='9')
        {
            sum=sum*10+(ch-'0');
        }
    }
    printf("%d",sum*2);
    return 0;
}